Model systems for studying carcinogenesis in human target tissues (bronchus, pancreatic duct, breast and colon) are being developed to link investigations using experimental animals with human cancer. Metabolism of chemical carcinogens is being studied in human tissues maintained in these model systems. For example, a marked variation among individuals in their capacity to metabolize carcinogenic polynuclear aromatic hydrocarbons has been observed. This interindividual variation may, in part, be due to genetic factors. Cultured human bronchi convert chemical carcinogens, e.g., benzo(a)pyrene, into metabolites that are mutagens in mammalian cells (V-79 cells). This mutagenesis assay is an important new screening test for chemical carcinogens. Chemical and physical carcinogens cause basal cell hyperplasia and atypical squamous metaplasia in cultured and xenotransplanted human bronchi. Model systems using human tissues should be useful in several areas of cancer research including: 1) identifying environmental carcinogens, their metabolic pathways and host factors determining susceptibility; and 2) testing new methods of prophylactic intervention in populations at high risk of developing cancer. BIBLIOGRAPHIC REFERENCES: Harris, C.: Chemical carcinogenesis and experimental models using human tissues. Beit. Pathol. 158: 389-404, 1976. Harris, C., Autrup, H., Stoner, G., and Trump, B.: Model systems using human lung for carcinogenesis studies. In Harris, C. (Ed.): Pathogenesis and Therapy of Lung Cancer. New York, M. Dekker Inc., 1977, In press.